The present invention relates to a device for inserting polygonal and shaped bars in the collet of a chuck of machine tools.
As is known, in most automatic bar-loaders for lathes the bar to be inserted in the collet of the chuck is arranged within a tubular guide and is pushed forwards by a bar pusher. When a high thrust force is required, the advancement system is constituted by a motor coupled to a worm screw.
This system has no disadvantages in the case of bars with circular cross section; vice versa, in the case of shaped bars, in order to allow insertion the profile of the bar and that of the collet must coincide during insertion. Even if the chuck is rotating, the bar in fact fails to enter the collet, since it is forcefully pushed against the non-complementary surface and it too is rotated, preserving an angular offset. On the other hand, even if the bar is not rotated, the moment during which it is in step with the collet is very short, and insertion is impossible since the advancement system has considerable inertia.